More film processors are investing in lines with nine or more layers. With more resin possibilities and combinations coming into play, it’s important to learn more about material rheology and compatibility, as well as die design.

OVERVIEW:
Film Extrusion

Film is divided into two subcategories: cast, or flat film; and blown film. In the former, hot plastic is extruded through a flat, slit die onto a polished chill roll where it is quenched, pulled to a second set of rolls to cool the other side, then wound. In blown film, plastic is extruded into a cylindrical die, then inflated to form a bubble, which is ultimately cooled and collapsed. Films can be either single or multi-layer. Most are based on polyethylene. Bags are one primary example of film extrusions.